Change implementation of API endpoints to use nachet-datastore for storing images and images related metadata

[MaxenceGui]

Issue Description :rocket:

With nachet-datastore currently in development, the backend will need to move from the Azure Blob Storage to store nachet-datastore for images and images metadata to nachet-datastore.

current:

sequenceDiagram
    nachet-frontend  ->> nachet-backend: REST
    nachet-backend ->> blob-storage: REST queries

desired:

sequenceDiagram
    nachet-frontend  ->> nachet-backend: REST
    nachet-backend ->> nachet-datastore: function calls
    nachet-datastore ->> ailab-db: postgresql queries
    nachet-datastore ->> blob-storage: REST queries

Acceptance Criteria ✅

• nachet-datastore is used
• Every reference to Azure Data Storage is move to the backend
• The endpoint for pictures batch import is tested and working

Tasks 🛠️

• [x] Move the azure-storage-api.py to nachet-datastore
• [x] Import nachet-datastore from GitHub directly
• [x] #85
• [x] #74

[rngadam]

@MaxenceGui let's discuss this in-person, the description needs some work.